Tough question, basicly if you do not race then most likely there is no need to upgrade cranks unless you just want to.

As for the teeth, if the new crankset has a larger big ring it will give you more top speed, this is only if you already top out your current chainring. If it has a larger small ring it will make climbing a little more difficult if you spend a lot of time in your small ring. If it is smaller it will allow you to spin faster on your climbs.

The crankset really is not one of the top things to upgrade if it is not broken. You would probably get more benefit out of upgrading tires than you would a crankset.

If you're rather large (like myself) you may notice upgraded cranks are a bit stiffer. I exchanged the Shimano Alivios that came stock on my Fuel with Race Face Evolve DH'ers, and noticed a pretty big difference, but in most cases (unless you're racing or really hard on equipment), your money would be better spent closer to the wheels/tires.

<phew!> I think you guys just saved me $80 bucks! Was about to bid on a Truvativ crankset.

My goal is to make my ride faster/lighter! I've got an entry level sporting goods store bike (not worth mentioning) with DS and am hankering to make it even better. I've seen posts where you guys don't recommending upgrading these copycats but if quality components are super cheap (ebay) its really tempting to do so.

Thanks for the advice, I'll see if there are some quality wheels & tires that I can get for a steal in an auction. My idea is to upgrade stuff and eventually port it over to another bike or just keep this one and get a whole new bike later on.

BTW..any recommendations for a wheel/tire combo? I'll be mostly riding non-technical trails (bunnyhops at the most)

You aren't going to like this reply but basicly on that bike if it ain't broke don't fix it. You will be much better off putting the money in your piggy bank and putting it towards a Rockhopper, low line trek, Giant, KHS or something along those lines. It will definately pay off.

I too would recommend upgrading your frame first (better cranks/bb will likely be included), but there are advantages to high end cranksets. I consider crank arm length and chainring size to be a subjective choice so I won't really address those issues. However, better quality rings aren't as likely to bend, stiffer and stronger crank arms translate to less flex and more efficient use of pedalling energy (as is the case with splined v. square taper bottom brackets) with better durability, and better bottom brackets mean fewer replacements. I upgraded from Shimano Alivio to Race Face Prodigy XC's on my old Kaitai and couldn't believe the improvment. Much stiffer and I never bent a chainring. The big ring on my old crankset was constantly bent to where I'd have to use a tool to straighten it so it wouldn't bind on the chain againts the middle ring. with the Race Face, I could (and still do) slam my big ring into logs and have yet to bend it. Also, the Race Face splined bottom bracket (can't remember exactly which model) is super high quality, chances are it will last several seasons longer than a Shimano UN-52 or 72 for example. I installed all Race Face components on my Cove "Handjob" and have ridden it hard ever since (about 2 years) and still see no signs that my cranks/rings or bottom bracket need replacement.

Depends on what you're going to be doing. When I first bought my GF Opie, I did a lot of drops and such and went through 2 sets of cranks before I broke down and bought some better one. Sure did make a big difference.

You aren't going to like this reply but basicly on that bike if it ain't broke don't fix it. You will be much better off putting the money in your piggy bank and putting it towards a Rockhopper, low line trek, Giant, KHS or something along those lines. It will definately pay off.